This project aims to construct a publicly available dataset of net migration estimates (2000-2010) by age, sex, race, and Hispanic origin for all US counties and to provide access to these data for a broad community of researchers and practitioners through an interactive website for on-line mapping and analysis as well as data download. Because the estimates will be produced using a vital statistics version of the forward cohort residual method based on enumerations from Census 2000 and 2010 and birth and death counts from the National Center for Health Statistics, they do not rely on sampling and will be highly accurate and reliable. Each set of age-sex-race/Hispanic origin specific migration estimates will be derived by subtracting a measure of natural increase from population change over the period, with positive or negative differences being attributed to net migration. The project will integrate these 2000 to 2010 data with similar net migration estimates produced each decade since 1950 to produce an integrated longitudinal dataset providing 60 years of age-specific net migration for each US County. The entire dataset will be publically available for download and analysis on a unique and accessible website that allows for interactive custom mapping, chart-making, table construction, and data download. Selective migration by age, race/ethnicity, and sex alters counties' population composition, which has significant implications for health care provision and staffing, service infrastructure development, economic and labor market conditions, and fertility and mortality outcomes. In particular, the spatial distribution of age-specific migration influences the age structure of communities with significant implications for population aging, child health, education, and economic well-being and corresponding needs for health and social services. Accurate net migration estimates by detailed demographic characteristics are essential for research analyzing place- based age-specific migration patterns and for practitioners planning for public health services, civic infrastructure, and community and economic development. The data this project produces will be critically important for research on a variety of policy-relevant topics, including migration of the baby boom cohort and corresponding changes in community health care needs, exurbanization, the aging of the rural population, regional shifts in the migration of Hispanics and African-Americans, the persistence of high out-migration regions, young adult migration patterns, and the role of migration in the growth of amenity and retirement areas. Moreover, the proposed set of county-level net migration estimates are vital to applied demographers making small area population estimates and projections. The project is particularly important because without the proposed data, there will be no reliable county level migration estimates for the post 2000 period due to the demise of the long form of the Census and the limited sample size of the American Community Survey.